In conventional variable electronic impedance circuits of the type described, for example, in Japanese Laid-open Patent Specification No. 116,052/1977, there often occurs the problem of abnormal radio frequency (RF) oscillation, particularly immediately after the closure or turn-on of a power supply switch, resulting in distortion in the output of the associated receiver circuit.
The cause of the above problem has been determined to be the fact that since such a variable electronic impedance circuit has a feedback path, positive feedback always takes place in the feedback path upon the closure of the power supply switch, resulting in the above-related abnormal oscillation of the radio frequency signal.